Air compressor



Patented Aug. 20, 1946 UNITED STATES PATENT OFFICE j f y K Y 2,406,262 AIR COMPRESSOR Phil-ip L. Crittenden, Edgewood, Pa., assgnor to4 The Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Application December 28, 1943, Serial No. A515,92) 1o claims. 4(o1. 23o-184) This invention relates to fiuid compressors and more particularly to: the reciprocating piston type. l y

In compressors of the conventional type,v it has been found necessary to have a. certain amount of dead space for clearance between the piston and the cylinder head and in the valve chambers. This space retains a quantity of fluid at a pressure substantially above-they fluid pressure of a storage reservoir or receiver, whichV iiuid must expand during the intakestroke until the pressure in the Y cylinder is substantially below atmospheric pressure before the inlet valve will open to supply uid to the cylinder for the. inlet stroke. This cond-ition results' in lowered volumetric eiiiciency because of the unproductive piston movement and thediminished quantity of fluid delivered by the compressor to the receiver.

It is an object of this invention, therefore, to provide an improved compressor of the reciprocating piston type so designed that thev inlet and discharge valves will be positioned promptly for the intake movement of each piston and thereby to increase the volumetric efficiency of the compressor.

Another object is to provide a "compressor having a plurality of fluid compressing cylinders in which one cylinder will be supercharged with a certain amount of iiuid under pressure from another cylinder before the beginning ofv the intake stroke of the piston in the first' mentioned cylinder.

In the accompanying drawing the single' figure isa vertical sectional view of a fluid compressor constructed in accordance with this invention.

As shown in the drawing, the compressor may comprise a casing, designated by the numeral I having secured to the bottom surface thereof in a suitable manner a crankcase 2 in which there is rotatably mounted the usual driven crankshaftv 3. The right-hand end of the casing I, as illustrated, is provided with a cylinder 4 in which a piston 5 is slidably mounted toy be reciprocated by thecrankshaft 3-through the medium of the connecting rod 6. The left-hand end of the casing I is provided with, a cylinder 1 in which apistony 8 issimilarly mounted and reciprocated likewise through the medium of a connecting rod' 9.

l Secured to the top` surface of the casing I byA bolts or other suitable means is a cylinder head I0- which provides valve controlled inlet and discharge passages for the iiuidr compressed in a manner hereinafter more fully described.V A fluid compressing chamber I I is thus defined at'thev right hand end' of the casingby a portion of the Y the chamber 21 Y 2v e y g c. bottom surface of thehead IIJ', the Wall of the cylinder 4 and the top surface of the piston. 5. In a similar manner a, uid compressing-chamber I2 isv definedV at the left hand endv of the casing by another portion of the bottom surface of the head I0, the wall of the cylinder 'If and the top surface of the piston 8.

Formed in the bottom face of the cylinder head I IJ and located between the two portions just mentioned is a recess I 3 which communicates with the compressing chamber II'by way of a valve controlled passage I4 in the head and with the compressing chamber I2 by way of a Valve controlled passage I5V in the head. This recess is open at theV bottom toA a vertical bore IB formed in the wall between the cylinders 4 and I of the casing I.

Slidably mounted in the bore I 6 is a piston valve member I'I, the upper end` of which is provided with a frusto-conically shaped valve I8. This valve is arranged to engage a corresponding valve seat I9 which defines a portion of the recess I3` and to thereby close communication between passages I4 and I 5. Interposed between and operatively engaging the bottom of the bore I6 and the lower end of the valve member I"I is a helical spring 2Q which constantly exerts an upwardlyl directed force on the valve member.

Thel lower end of the valve member I'I is provided with an actuating stem 2| which is slidably carried in a vertical bore 22 in the casing I and extends through bore 23 in the crankcase 2 into the crankcase chamber 24. Securedto the lowerend of the stem 2| member 26 which projects of both pistons so as to by a nut 25 is a cross'- into the paths of travel be engaged and moved downwardly by either piston against the oppas# ing pressure of spring 2U.

Atthe extreme right-hand end of the cylinder' head I0 there is formed a discharge chamber 2`I which extends vertically through the' head andy is in constant open communication with a uid discharge pipe 28. Y This chamber is closed at the top by a hollow nut member 29 which has screwthreaded engagement withr the cylinder head I-U. The nut member is providedA with a vertically cylindrical sleeve andv which servesl as a guide and a stop for the discharge valve 3 I .v preferably of the tapered mounted in vthe chamber poppet type is operably chamber 21.

SI is a vertical guide stem 32 which is slidportion 3U which extends intol I'his valve;

21. and controls com munication between compressing cliamber I land head'IIL Y 'vr-Above the valve fa; wall: 4I which defines the bottom ofthe chamably guided in the sleeve portion 30 of the nut member 21. VInterposed between and operatively engaging the nut member 21 and the back surface of the valve 3I is a helical spring 33 which, when the piston substantially completes its upwardrstroke, urges the valve downward into Y sealing engagement with an annular tapered seat 34 formed in the bottom of thel chamber 21'as illustrated,` to interrupt the flow of fluid under pressure'from the compressing chamber II.

To the left of the chamber 21 there is formed ingthe cylinder head I0 an inlet chamber 35` which is in constant communication with a fluid inlet passage 36 which is in open communication with an inlet pipe 31. This chamberl is closed unseated position fluid under pressure may flow from compressing chamber I2 to compressing chamber II by way of passage I5, recess I3 andY passage I4 for reasons which will hereinafterV With the piston positioned more fully appear. as just described the inlet and discharge valves will be in their seating positions as shown.

HUpon rotation of the crankshaft 3,c0nnecting".v rod'B and' thereby piston 5 will'. be moved upwardly. In response tothe upward travel of Vthe piston the compressed spring will act to move the valve member I1 upwardly until valve at the top by a nut member '38 which has screwe threaded engagement Iwith the headv I6. The

communication between the bottom of the chamber 35 and the compressing chamber lIl may bev closed,vas illustrated,"by a valve 39, preferably of the poppet type, which is arranged to seat on a. valve seat 48 formed in thelower side of the 39the head I 0 is provided with herr-.35 andwhichis provided with an' upwardly extending Vsleeve portion 4Ia `in which there is slidably mounted the guide vste'm42 of the lvalve 'thereby urging the' valve 39 into sealing engagement with the Valve seat 4I).

-'Attention is here directed to the fact that the members employed for imparting resiliencyv to the movement of the valves are disposed in the cylinder head and not Vin the compressing chamber, thereby keeping rthe necessary clearance space between the piston and the head at a minimum and thereby'adding to the volumetric efciencyofthe compressor.

At the left-hand .end of the compressor, the head I is provided with aninlet and discharge valve construction for cooperating with cylinder 1 similarto that described above for cylinder 4. At the extreme left-hand end of the cylinder head I0, forV controlling the ow of fluid to and from the .compression chamber I2, thereis provided a; discharge valve mechanism and an inlet valve'mechanism, each of which Yis identicalwith thercorresponding mechanism mounted in the right-hand end of theA cylinder head. In view of the similarity; the several parts of thesemechanisms will be indicated by the same reference numerals a's applied tothe mechanisms atthe right handend of the casing with the exception that the prime sign is added. 1 kIn operation, when the crank shaft 3 is lturned by any suitable source of power, pistons 5 and 8 will be actuated by the connecting rods 6 and 9, respectively. Each piston completes an inletand a discharge stroke for each revolution of the crankshaft. y '.In the accompanying drawing, piston 6 is shown in its upper'dead center position and piston 5 is shown in its lower dead center position. TheA piston 5 in this position acts through the medium of the memberl26 and stem 2| of the valve member to hold valve I8 out of engagement with valve seat'I9. Upon movement of the valve I8 to its I8 again engages valve seat I9 and closes coml munication between chambers II and I2.

It is preferred that the piston movement required to permit the valve memberV I1 to seat be relatively small so 'that there will be little reverse 'fluid flow after'the pressures of fluid Vin the two rcompressing chambers have equalized.

The piston 5 as it moves upwardly compresses therfluid in the chamber II until the Yupwardly directed'force exertedfbythe fluid V0n the dis*- charge 'valve 3l un'seats the Vvalveaga'inst the combined downwardly directedrforce exertedwb'y the spring 33 and the fluid Vpressure vwhich may be in the discharge pipe 28. With valve'3I'unseated, fluid will flow from chamber II into dis- Y charge-chamber 21and thence into discharge pipe 28 anda suitable fluid receiver, notV shown. Fluid under pressure will continue to flow in this manner until the piston-5 nearly'reachesrtheend of its upward stroke when,V with the uid pressures in the discharge pipe 28and the chamber 5 substantially'equal, the force of the s'pring33- Y will prevail and the valve 3I"'Wil1 again be seated. Y Y At the same time 4aspiston 5 is making its up- Y ward stroke, piston 8-will be'making its downward stroke. At the startY of the stroke the inlet and discharge valves are positioned as shown in the accompanying drawing. After a slight down'- ward movement ofthe piston, pressure of fluid in chamber l2 will be'sufciently below atmosphere to allow the pressure of fluid inthe inlet chamber 35 to move valve 39 against the 'pressure ofspring 44 and away from the valve seat,Y

49'. Fluid will flow' through inlet vpipe 31 and passage 36 to inlet chamber 35 and thence past the valve-seat 49 to compressing chamber I2. The pressure" of inowfing fluid will hold valve 39' unseateduntil the piston Y8 nears the end of its downwardV movement. As the' piston'nears the end of its stroke'the -valve W'ill `aga'inwbe seated by spring 44.

. Shortly after the inlet valve is seated, thevbottom yof the piston 8 will engage the cross-member 26 andv move it downward which will likewise move'the valve member Vl1 downward thereby moving the valve I8 away from valve seat I9.

The discharge valve 3I will also have been seated before the piston 8 engages the cross-. member 26. Fluid under pressure will now flow from compressing chamber IIV to compressing chamber I2 by way of passage I4, recess I3,l and passage I5.

The piston 8 will now be at bottom dead center while the piston 5will beat top dead center. f'rlgleV Y valves will be in the position as illustrated@` The same operation will follow as previously described except that the function performed by piston 5 will now bel performed4 bypiston 8 andviceversa 1 At the completion of each compression v stroke or inlet stroke, valve member'. l1. will operate to open communication between the two compresse. ing chambers. /Thu'sthe pressure of Yfluid ina.

compression chamber is reduced before the beginning of an inlet stroke of its piston and is increased before the beginning of a compression stroke.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

l. In a luid compressor of the type comprising two pistons and means connected to said pistons for actuating irst one and then the other to compress fluid, in combination, a communication for permitting fluid to flow between the pressure sides of said pistons, a valve for opening and closing said communication, means for effecting the operation of said valve to open said communication as an incident to either piston reaching substantially the end of its inlet stroke, and means for effecting the operation of the valve to close said communication at all other times.

2. In a fluid compressor of the type comprising two pistons and means connected to said pistons for actuating rst one and then the other to compress fluid, in combination, a communication for permitting fluid to flow between the pressure sides of said pistons, a valve for opening and closing said communication, resilient means for actuating said valve to close said communication, and means operative by either of said pistons at substantially the end of its inlet stroke to actuate said valve to open said communication.

3. In a uid compressor of the `type comprising two pistons, and means connected to said pistons and operable to actuate first one and then the other to compress fluid, in combination, a communication connecting the pressure sides of the two pistons, valve means controlling said communication, and means conditionable upon the movement of either piston to substantially the end of its inlet stroke to actuate said valve means to open said communication, and means operative to actuate said valve means to close said communication at all other times.

4. A fluid compressor comprising two pistons, means connected to said pistons to actuate first one and then the other of said pistons to compress fluid, a communication connecting the chambers on the pressure sides of the two pistons, valve means controlling said communication, means for actuating said valve means to close said communication, and means operative by each piston at substantially the end of its inlet stroke to actuate said valve means to open said communication.

5. A uid compressor comprising two pistons, means connected to said pistons to actuate first one and then the other of said pistons to compress fluid, a communication connecting the chambers on the pressure sides of the two pistons, valve means controlling said communication, means conditionable upon movement of either piston to substantially the end of its inlet stroke to actuate said valve means to open said communication, and means operative to actuate said valve means to close said communication at all other times.

6. A uid compressor of the type arranged to draw uid into one chamber for compression therein while uid is being compressed in another chamber and comprising two fluid compressing chambers and two pistons for reciprocating in the respective chambers, in combination, means for supercharging each of said chambers with iiuid under pressure, the supercharging means comprising means rendering the supercharging means ineffective until either piston is substantially at the end of its inlet stroke and operative by the piston as it approaches the end of its inlet stroke to render said supercharging means eifective.

7. A iluid compressor of the type arranged to draw fluid into one chamber for compression while fluid is being compressed in another chamber and comprising two pistons for reciprocating in the respective chambers, in combination, means for preloading the pressure side of a piston, completing its inlet stroke, with fluid under pressure from the pressure side of a, piston completing its compression stroke, and means actuable by either piston at substantially the end of its inlet stroke to render said preloading means operative, and means separate from said piston for actuating the second mentioned means to render the preloading means ineifective.

8. A fluid compressor of the type arranged to draw uid into one chamber for compression while fluid is being compressed in another chamber and comprising two pistons for reciprocating in the respective chambers, in combination, means for preloading the pressure side of a piston, completing its inlet stroke, with fluid under pressure from the pressure side of a piston completing its compression stroke, and means conditionable upon the movement of either piston to substantially the end of its stroke for rendering said preloading means operative.

9. A uid compressor of the type arranged to draw iluid into a chamber for compression vtherein while fluid is being compressed in another chamber and comprising two fluid compressing chambers and two reciprocating pistons for compressing uid in said chambers, in combination, means for venting fluid under pressure from one chamber, valve means operative to start and stop said venting action, means conditionable upon the movement of either piston to substantially the end of its inlet stroke to actuate said Valve means to start said venting action, and means operative to actuate said valve means to suspend said venting action at all other times.

10. In a fluid compressor of the type comprising two pistons and actuating means connected to said pistons for compressing fluid with first one piston and then the other, in combination, a

passage in open communication with the pressure side of` one of said pistons, a passage in open communication with the pressure side of the other of said pistons a communication for permitting fluid to flow from one of said passages to the other, valve means for controlling said communication, resilient means actuating said valve means to close said communication, and means operable by either of said pistons at substantially the end of its inlet stroke to cause said valve means to open said communication.

PHILIP L. CRI'I'TE-NDEN. 

